During the preparation of integrated circuit modules, input/output (I/O) pins are inserted into the substrate so as to protrude from one surface of the substrate known as the bottom side, for insertion into circuit cards or circuit boards. The pins also protrude slightly from the other surface referred to as the top side so as to contact the circuitry on the top side which, in turn, connects to the integrated circuit chip or chips which are subsequently connected to the substrate or carrier. When the pins are to be connected to the substrate circuitry by a soldering process, solder flux compositions have been applied to the pins.
Solder flux compositions are employed to remove oxides from the pins and to prevent the pins from oxidizing when subjected to elevated temperature for soldering and thereby serving to maintain the electrical conductivity of the pins.
Once the solder is applied, any flux composition or residue therefrom, (e.g., unpolymerized species) remaining on the pins and substrate must be removed to provide as clean a substrate as possible. This involves a cleaning step which normally employs an organic composition such as N-methyl pyrollidone or a halogenated hydrocarbon such as perchloroethylene in the case of rosin-base flux compositions.
In addition, integrated circuit chips are attached to the integrated substrate or carrier by applying solder to preselected areas on the substrate which is generally referred to in the art as the "chip pad area". Such areas can be defined, for instance, by providing preselected exposed areas of a metal such as copper which will accept the solder. Moreover, a flux composition would normally be applied to the substrate to facilitate the application of the solder to the chip pad area. After solder is applied to the chip pad area, any flux and/or flux residue must be removed prior to attaching the integrated circuit chip so as to provide as clean a module as possible.